Effectiveness of the 10-valent pneumococcal non-typeable <i>Haemophilus influenzae</i> protein D conjugate vaccine (PCV10) against hypoxic pneumonia in children in Maha Sarakham Province, Thailand.

Hypoxic pneumonia is a major cause of morbidity and mortality among children in low- and middle-income countries. This study evaluated 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PCV10) effectiveness in preventing hypoxic pneumonia among children in Maha Sarakham Province, Thailand. We conducted a retrospective case-control study using medical records from Maha Sarakham Hospital between January 2020 and December 2022. Cases were children aged 1 month to 5 y hospitalized with hypoxic pneumonia; controls were hospitalized with non-hypoxic pneumonia. PCV10 vaccination status (unvaccinated, incomplete [1-2 doses], or complete [≥3 doses]) was compared. Vaccine effectiveness (VE) was estimated using logistic regression, with propensity score adjustment and multiple imputation to address confounding and missing data. Among 398 children hospitalized with pneumonia, 207 (52.0%) had hypoxic pneumonia and 191 (48.0%) had non-hypoxic pneumonia. Overall vaccine coverage was low: 18.3% were fully vaccinated, 3.5% partially vaccinated, and 78.1% unvaccinated. The unadjusted VE against hypoxic pneumonia was 28% (95% CI: 3-55%; P < .001). After propensity score adjustment, VE increased to 31% (95% CI: 8-62%; P < .001). Using multiple imputation, the unadjusted and adjusted VE were 34% (95% CI: 5-61%; P < .001) and 35% (95% CI: 4-65%; P < .001). In conclusion, PCV10 vaccination was associated with a reduced risk of hypoxic pneumonia among Thai children. These findings support the integration of PCVs into national immunization programs and underscore the importance of achieving and maintaining high vaccine coverage to prevent severe pediatric pneumonia.